Deleted device manager's inside global cache and changed to use the topo cache.
The reason is it caused some unmatched condition with the topo cache when link and port status was changed.
The DeviceEvent timing is changed.
The old one sends it when it is appeared, or attachment point or IP is changed, but now it sends every packet-in to update last-time-seen.

Note:
Looks like there is some vulnerability for changing the mastership of switches.
During mastership changes, the intent reroute is occured, and for a short period of time links or ports haven't found,
so the intent cann't calcurate its path.

Change-Id: I311fa5ad368ca833915999ad112274f1a7979387
diff --git a/src/main/java/net/onrc/onos/apps/forwarding/Forwarding.java b/src/main/java/net/onrc/onos/apps/forwarding/Forwarding.java
index d955828..03c9740 100644
--- a/src/main/java/net/onrc/onos/apps/forwarding/Forwarding.java
+++ b/src/main/java/net/onrc/onos/apps/forwarding/Forwarding.java
@@ -560,6 +560,8 @@
                     break;
                 case STATE_CHANGED:
                     IntentState state = pathIntent.getState();
+                    log.debug("This is STATE_CHANGED. intent id {} is now state {}",
+                            pathIntent.getId() , state);
                     switch (state) {
                         case INST_REQ:
                             break;